I disagree. Letting apache near any decent webserver setup is a bad idea. PHP-FPM actually handles it better in my opinion. If you have Ubuntu, nginx even maintain their own PPA for php. So you can install php-fpm with one command.

Also, if you're going to use an opcode cache, my money is on APC (which is developed alongside php). Xcache is lighty's module and having used it, I can honestly say, it sucks.

As I said above, if you have a small to medium site, having over two worker processes is useless. They will just sit there eating ram, albeit a very small amount.